I've never tried to mirror the drives, but I do know that the drives are keyed to the mac address on the IPEX, so if they don't have the correct license key, they will not run. You could probably see more of what is going on if you plug in a monitor and keyboard to the IPEX. The only way I know of to successfully replace a drive is to take a drive that has the same version software loaded on it and then restore your data base to the new drive, assumming you have a backup of your original drive.
You may not have a drive problem, using the monitor will tell you more.

TG